The laser dye Coumarin 343, 1H,5H,11H- (1) -benzopyrano- (6,7,8-ij) quinolizin-10-carboxylic acid-11-one-2,3,6,7-tetrahydro-11-oxo, 1, was prepared. Several secondary peresters of 1 were generated in situ and the chemiluminescence observed from the decomposition of the peresters was studied. The quantum yield of chemiluminescence was very low in all cases, and seemed to vary inversely with the strength of the alpha carbon-hydrogen bond. The peresters were generated using two methods: reaction of the acid chloride of 1, 19, with the hydroperoxides, and also through the action of such esterifying agents as dicyclohexylcarbodiimide (DCC) and carbonyldiimidazole (CDI). The chemiluminescence quantum yields using the esterifying agents were similar to or lower than the quantum yields obtained from the reactions of 19 with corresponding hydroperoxides.The alpha-keto acid 2 was prepared in an attempt to increase the chemiluminescence quantum yield by changing the pathway of decomposition of the perester. Unfortunately, the fluorescence efficiency of 2 is greatly diminished as solvent polarity increased, so very little chemiluminescence was observed from peresters of 2. The strong solvent-dependent quenching is believed to be due to a highly polarized excited state, possibly involving a nonemissive twisted intramolecular charge transfer (TICT) geometry.